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Repair


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Content:

Preface

I strongly recommend that you try to repair your Electric Mistress only if you have sufficient knowledge in electronics. You can easily damage the BBD which is no more available as spare part which means your Mistress is irreparable damaged.
The following instructions are dedicated as help for experienced electronic technicians.

I reccomend to get your Electric Mistress repaired by Howard Davis or or contact Electro-Harmonix for an authorised repair shop.

Tools required:

You will need a frequency generator and an oscilloscope. A frequency counter helps, but is not essential. ESD protection is mandatory.

Voltage Regulation

The non-Deluxe versions work with batteries or AC-adapter. For the AC-adapter The Mistress has a nowadays uncommon 3.5 mm (1/8") jack socket. The tip of the jack plug is the positive pole; the sleeve is the negative pole. As AC-adapters today have coaxial power connecters, musicians need to make a coaxial/jack adapter or need to cut the coaxial connector from the AC-adapters and attach a jack plug to it. By this it can easily happen that the poles get swapped and the Mistress is fired by reverse polarity. Reverse polarity may damage lot of parts in the Mistress, mainly the electrolytic or tantalum capacitors, the integrated circuits and even the transistors.

If the voltage regulation had been damaged e.g. by reverse polarity you may either keep it vintage or modernize it. When keeping it vintage you sholud replace only broken parts and stick to the same parts and values as the original and add the PSU Mod. To modernize it you can replace the whole voltage regulation by something similar to the reissue versions. It depends on your repair philosophy. Modernizing the voltage regulation will improve reliability and give a better protection for the BBD but it may change the sound (rather insignificant or not at all) and will surely reduce the collectors value.

vr mod

Trouble Shooting Sequence V2, V3, V4, V5

See also the measured voltages of my Electric Mistress V2 for reference.

  1. Remove the SAD1024 (caution for ESD) - make sketch or photo to remember orientation
  2. Turn on power supply and check for 18.0 V at pin 7 LM741
  3. Check for 12 V (12.0 - 13.5 V) at pin 8 4885, pin 14 4013, pin 3 LM339
  4. Check for a low frequency (~0.05 - 20 Hz) sweep about 0.5 to 9 V at pin 2 LM339 - frequency controllable by RATE pot
  5. Check with oscilloscope for clock output at pin 1 of LM339 (~40 kHz to 400 kHz)
    Switch to FILTER MATIX mode. Clock frequency must be controlled by RANGE
  6. Check with oscilloscope for square wave output at pins 9, 12 and 13 of 4013 (~20 kHz to 200 kHz)
  7. Input a 200 Hz signal. Follow signal pin 5 -> pin 7 -> pin 2 -> pin 1 of 4558
  8. Check SAD1024 socket:
    • pin 1: GND
    • pin 2: input signal (x2 amplitude)
    • pin 3: clock square wave
    • pin 4: GND
    • pin 5: 12 V
    • pin 6: n/a (will be the output)
    • pin 7: 12 V
    • pin 8: clock square wave
    • pin 9: 12 V
    • pin 10: clock square wave
    • pin 11: 12 V
    • pin 12: n/a (will be the output)
    • pin 13: GND
    • pin 14: clock square wave
    • pin 15: input signal (x2 amplitude)
    • pin 16: GND
  9. Put back the SAD1024 into socket (double check orientation)
  10. Adjust bias trim until signal is found at pin 6 and 12 of SAD1024
  11. Check signal at output
  12. Align device

Trouble Shooting Sequence V6

  1. Remove the SAD1024 (caution for ESD) - make sketch or photo to remember orientation
  2. Turn on power supply and check for 9.0 V at pin 4 LM324
  3. Check for a low frequency (~0.05 - 20 Hz) sweep at pin 8 LM324 - frequency controllable by RATE pot
  4. Check with oscilloscope for clock output at pin 7 of LM324 (~40 kHz to 400 kHz)
    Switch to FILTER MATIX mode. Clock frequency must be controlled by RANGE
  5. Check with oscilloscope for square wave output at pins 1, 5 and 2 of 4013 (~20 kHz to 200 kHz)
  6. Input a 200 Hz signal. Follow signal pin 3 -> pin 1 -> pin 6 -> pin 7 of 4558
  7. Check SAD1024 socket:
    • pin 1: GND
    • pin 2: input signal (x2 amplitude)
    • pin 3: clock square wave
    • pin 4: GND
    • pin 5: 9 V
    • pin 6: n/a (will be the output)
    • pin 7: 9 V
    • pin 8: clock square wave
    • pin 9: 9 V
    • pin 10: clock square wave
    • pin 11: 9 V
    • pin 12: n/a (will be the output)
    • pin 13: GND
    • pin 14: clock square wave
    • pin 15: input signal (x2 amplitude)
    • pin 16: GND
  8. Put back the SAD1024 into socket (double check orientation)
  9. Adjust bias trim until signal is found at pin 6 and 12 of SAD1024
  10. Check signal at output
  11. Align device

 

Trouble Shooting Sequence Deluxe V1, V2, V3

CAUTION! This devices works with high voltage. By openening the case you constitute a risk of lethal electric shock.

  1. Remove the SAD1024 (caution for ESD) - make sketch or photo to remember orientation
  2. Turn on power supply and check for 15.0 V at pin 3 (out) of 78L15
  3. Check for a low frequency (~0.05 - 20 Hz) sweep at pin 8 LM324 - frequency controllable by RATE pot
  4. Check with oscilloscope for clock output at pin 7 of LM311 (~60 kHz to 2000 kHz)
    Switch to FILTER MATIX mode. Clock frequency must be controlled by RANGE
  5. Check with oscilloscope for square wave output at pins 1, 5 and 2 of 4013 (~30 kHz to 1000 kHz)
  6. Input a 200 Hz signal. Follow signal pin 2 -> pin 6 LM741, pin 2 -> pin 1 of 4558
  7. Check SAD1024 socket:
    • pin 1: GND
    • pin 2: input signal (x2 amplitude)
    • pin 3: clock square wave
    • pin 4: GND
    • pin 5: 15 V
    • pin 6: n/a (will be the output)
    • pin 7: 15 V
    • pin 8: clock square wave
    • pin 9: 15 V
    • pin 10: clock square wave
    • pin 11: 15 V
    • pin 12: n/a (will be the output)
    • pin 13: GND
    • pin 14: clock square wave
    • pin 15: input signal (x2 amplitude)
    • pin 16: GND
  8. Put back the SAD1024 into socket (double check orientation)
  9. Adjust bias trim until signal is found at pin 6 and 12 of SAD1024
  10. Check signal at output
  11. Align device

 

Trouble Shooting Sequence Deluxe Reissue V4, V5

CAUTION! This devices works with high voltage. By openening the case you constitute a risk of lethal electric shock.

  1. Remove the RD5106A (caution for ESD) - make sketch or photo to remember orientation
  2. Turn on power supply and check for 12.0 V at pin 3 (out) of 78L12
  3. Check for a low frequency (~0.05 - 20 Hz) sweep at pin 8 LM324 - frequency controllable by RATE pot
  4. Check with oscilloscope for clock output at pin 7 of LM311 (~100 kHz to 1000 kHz)
    Switch to FILTER MATIX mode. Clock frequency must be controlled by RANGE
  5. Check with oscilloscope for square wave output at pins 1, 5 and 2 of 4013 (~50 kHz to 500 kHz)
  6. Input a 200 Hz signal. Follow signal pin 2 -> pin 1 -> pin 6 -> pin 7 of 4558
  7. Check RD5106A socket:
    • pin 1: clock square wave
    • pin 2: GND
    • pin 3: n/a
    • pin 4: n/a (will be the output)
    • pin 5: n/a (will be supplied by BBD with ~ 10 V [VDD - 2 V])
    • pin 6: input signal
    • pin 7: GND
    • pin 8: 12 V
  8. Put back the RD5106A into socket (double check orientation)
  9. Check signal at output
  10. Align device

 

 
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